Manufacture of metal containers with rimmed opening

ABSTRACT

An open-ended container is produced utilizing as a starting material a unitary drawn sheet metal container body which has a substantially circular endwall, a sidewall and a curved portion joining the two. This is achieved by full diameter blanking of the endwall. The blanking is carried out by the use of cooperating support and cutting dies. The support die is contoured to the interior of the container body. The cutting die contains a uni-diameter recess bounded by a cutting edge aligned with the sidewall of the support die. The resulting cut has a tapered configuration which facilitates curling of the sidewall in two steps to provide a rimmed opening.

United States Patent Saunders 1 Dec. 19, 1972 [5 1 MANUFACTURE OF METAL 232L085 6/1943 Hubbard.[ ..113/120 H CONTAINERS WITH RIMMED' OPENING FOREIGN PATENTS OR APPLICATIONS [72] Inventor: William T. Saunders weirton, w 5 10.370 8/1939 Great Britain ..1 13/120 H Primary Examiner charles W. Lanham [73] Assignee: National Steel Corporation Assistant Examiner -Michael-J. Keenan Filed: g 1970 Attorney-Shanley and O Neil [21] App]. No.: 61,312 [57] ABSTRACT An open-ended container isproduced utilizing as a 52 CL 113 G, 113/116 QA, 3 2 H, starting material, a unitary drawn sheet metal con- 7 113/120 AA tainer body which has a substantially circular endwall, 511 int. Cl. ..B21d 51/00 a sidewalland a curved Portim mining the This is [58] Field of Search] 13/1 G 1 H 1 16 A 1 16 DD achieved by full diameter blanking of the endwall. The 1 13/120 H 120 P 1 0 72/335 blanking is carried out by the use of cooperating support and cutting dies. The support die is contoured to the interior of the container body. The cutting die contains a uni-diameter recess bounded by a cutting [56] References cltd edge aligned with the sidewall of the support die. The UNITED STATES PATENTS resulting cut has a tapered configuration which facilitates curling of the sidewall in two steps to pro- Calleson 6t 8]. ..I H vide a rimmed opening 7 1,665,203 4/1928 Delf ..1 13/120 H 796,534 8/1905 Rigby ..72/336 6 Claims, 9 Drawing Figures PATENTEU DEC 19 I972 SHEET 1 0F 2 INVENTOR WILLIAM T. SAUNDERS ATTORNEYS PMENTEU DEC 19 I972 SHEET 2 0F 2 lNVENTOR WILUAM r. SAUNDERS FIG .8

ATTORNEYS 1 MANUFACTURE OF METAL CGNTAINERS WITH RIMMED OPENING This invention relates to the manufacture of openended containers. In particular it relates to the manufacture of drawn (1. The term drawn" is used herein to describe container bodies formed in single draw, double draw, drawn and ironed, and the like operations.) sheet metal containers useful as aerosol or screw top cans.

In the conventional manufacture of such containers, a sheet metal blank is drawn to provide a unitary container body of cup-shaped configuration having a substantially circular endwall joined at its periphery by a curved portion to a sidewall. At least a portion of the endwall isblanked from the body to provide an opening which is suitable for engagement with a container top. Usually before the attachment of the top, the metal adjacent the opening provided by the blanking is curled outwardly (2. Outwardly curling to form a rimmed opening is advantageous for a numberof reasons. It

eliminates from exposure the sharp edge at'the blanked opening. If the container body has been enameled or otherwise finished prior to blanking, the unfinished metal exposed due to blanking can be concealed by curling. In addition, curling provides a rim of increased strength so that the adjacent metal can withstand external pressure applied, for example, during capping.) to provide a rounded edge-protected rim.

The metal which is curled is stretched and may split. Splitting is especially a problem in the case of curling at small diameter openings where relatively low ductility container material is utilized. Such splitting is unacceptable from a commercial standpoint. I

An important objective of this invention is the production of open-ended containers from such container bodies in away that the'problem of splitting in the forming of rimmed openings is substantially eliminated notwithstanding use of a more economic low ductility material and rim formation at small diameter openings.

Referring to the accompanying drawings:

FIG. 1 schematically illustrates a prior art multi-step for forming a sheet metal container with a rimmed opening.

FIG. 2 is aschematic illustration of apparatus carrying out a developmental method of blanking.

FIG. 3 is a vertical sectional view illustrating preferred apparatus of this invention.

FIG. 4 is a vertical sectional view illustrating a variation in a portion of the apparatus depicted in FIG. 3 within the scope of this invention.

FIGS. 5-7 are vertical sectional views illustrating apparatus curling the sidewall of an open-ended container to provide a rimmed opening in accordance with this invention.

FIG. 8 is a fragmentary sectional view of a container manufactured utilizing the instant invention.

FIG. 9 is a fragmentary sectional view of a container manufactured utilizing a method within the scope of the invention and differingslightly from the method carried out by the FIG. 7 apparatus.

' In a prior art method for forming a sheet metal container with a rimmed opening, depicted in FIG. 1, a concentric portion of the endwall is blanked frompost portion ll) of a container body leaving in inwardly directed flange 12 bounding an opening 14 as shown in FIG. la. The endwall flange is wiped upwardly so that it becomes part of the container post sidewall forming a full diameter opening 16 shown in FIG. lb. The post sidewall is thencurled to provide rounded rim 18 as shown in FIG. 1c. The wiping up and curling steps involve considerable stretching in the metal constituting the upper portion of the container body.

Consider the expansion of the opening required when working on a one inch diameter post as shown, in FIG.'1. The diameter of blanked opening 14 is 0.8 inch. The diameter of opening 16 is one inch. The diameter of rim 18 is 1.2 inches. This means the inner edge of flange 12 has been stretched through at least fifty (50) percent. Many conventional container materials, especially high strength steels required for aerosol cans, are not able to withstand such circumferential stretching to the extent necessary for high production efficiency.

The present invention eliminates a major portion'of this expansion by providing commercially practicable full diameter cutting methods and apparatus.

One method for blanking a disc from the endwall of the container body which is not considered commercially practicable is disclosed in Calleson et al. U.S. Pat. No. 2,339,763 at FIGS. 18a and 48. Calleson et al. Utilize a perpendicular edged insert die (that is, with its endwall joining its sidewall at a angle) and an exterior die having a multidiameter recess with a larger diameter portion of the recess coextensive with the outside diameter of the container body post. One serious disadvantage of this apparatus is that the exterior die must be changed if the thickness of the container material is changed, as often occurs in commercial practice. In addition, this die is not useful for shortnecked container bodies.

The use of an outer die having a uni-diameter recess developed as a part of the present invention to blank the full diameter of an endwall eliminates the abovespecified disadvantages. However, an unacceptable phenomenon referred to as dog-legging occurs. This is shown in FIG. 2. Container body 20 of FIG. 2a has a substantially circular endwall 22 which is joined at its periphery by a curved portion 24 to a sidewall 26. The container body 20 is mounted on a conventional perpendicular edged insert die 28. Another die 39 outside the container body has a uni-diameter recess 32. Sidewall 34 of this recess is aligned with the sidewall 36 of the insert die and the internal surface of the container sidewall. The dies 28 and 3t) together with the container body 26 mounted on insert die 28 are shown in position just prior to blanking in FIG. 2a.

As shown in FIG. 2b the dies are moved together to complete the blanking operation. Failure to support the curved portion 24 of container body 20 during blanking results in a dog-leg 40, which is outwardly angled. Such a dog-leg remains in the sidewall and if not eliminated interferes with any succeeding curling step.

The present invention further involves use of a contoured insert support die 48 as shown in FIG; 3. This contoured support die in conjunction with a uni-diameter cutting die 30 provides full diameter blanking without any of the disadvantages discussed above.

A drawn sheet metal container body to be blanked with these dies is of cup-shaped configuration. It has a post portion 42 which is necked in from its main portion sidewall by a ledge d6. The post portion 42 has a substantially circular endwall 22 joined at its periphery by a curved portion 24 to a sidewall 26.

Support die 48 has an endwall 50 of circular perimeter and a sidewall 52. These are interconnected by a curved-contoured portion 54. This curved-contoured portion plays a key roll in the present invention in that it prevents dog-legging from occurring during the blanking operation.

Endwall 50 has an outer diameter substantially corresponding to the internal diameter of the container body adjacent to endwall 22. It contains a recess 56 for receiving a bolt 58 for attaching die 48 to a supporting structure (not shown).

Interconnecting portion 54 is outwardly convex. The radius of this convex portion substantially conforms to the radius of the inner surface of curved portion 24 of the container body.

Cutting die 30 has a uni-diameter circular recessed portion 32. The uni-diameter nature of the recess plays a key roll in the present invention in that it allows the same die to be used notwithstanding change in container thickness. Moreover, because of this feature, die 30 is useful for blanking a short-necked container.

Recessed portion 32 is positioned opposite endwall 50 of support die 48. It has a sidewall 34 which culminates at the working end of the die in a circular cutting edge 60. The sidewall 34 and the cutting edge 60 are aligned with sidewall 52 of support die 48.

The container body is mounted on and supported by die 48. Sidewall 34 and cutting edge 60 of die 30 are aligned with the inner surface of sidewall 26 of the container body. Die 30 is moved'in the direction of die 48 until it blanks endwall 22 of the container body. A clean line of shear as represented by dotted lines 62 is obtained. The blanking is carried out without doglegging or other disadvantages occurring.

In FIG. 4 the interconnecting contoured portion 54 of support die 48 is beveled instead of outwardly convex. Die 48 is dimensioned so that when it is inserted in a container body, the beveled portion is opposite the inner surface of the curved portion of the container body. Withthis embodiment also, full diameter blanking is carried out without dog-legging occurring.

Blanking with the apparatus of FIGS. 3 or 4 produces open-ended container body with a sidewall which is of tapered configuration. As shown in FIG. the upper portion of the container sidewall 26 progressively decreases in thickness toward a tapered edge 63 at the blanked opening. This tapered configuration facilitates curling by providing a thinner sidewall portion which is curled initially. This thinner portion curls more easily with less likelihood of splitting than a straight sidewall.

Carrying out curling in two steps minimizes the occurrence of splitting. The first step provides strength for the second step. The second step provides the ultimate curl.

FIG. 5 shows apparatus for carrying out the first step. It includes a support die 66 and a curling die 68. Die 66 has an annular configuration. It is dimensioned so that during operation its outer surface 67 supports container body sidewall 44 and edge 46 and its inner sur-'- face 68 is aligned with the inner surface of post sidewall Curling die 68 has a centrally located projection 70' 72 terminates at its upper end in a curling'contour 74 which has the same radius as that desired for the initial curl.

FIG..6 shows the operation of this apparatus. Die 68 is moved toward the container body mounted on die 66 so that contour 74 curls the upper portion of sidewall 26 moving edge 63 and the tapered portion leading .to this edge outwardly and downwardly. The formed curl has a radius which is less than 75 percent, preferably less than 65 percent, of the radius of the final curl. Preferably, this initial curl has a radius which is more than 30 percent of the radius of the final curl. This initial curling step may be referred to as hemming. The initially formed curl or hem imparts sufficient strength in the vicinity of the top opening so that the final curlcan be formed without splitting occurring in the metal adjacent the opening. The tapering in the container sidewall coacts in this heniming tominimize the possibility of splitting.

FIG. 7 shows apparatus for the second curlingstep. It

comprises a support die 66 and a curling die 80. Die 66 is dimensioned the same as the support die used in the hemming step. The same support die can be utilized for both curling steps.

Die has a circular cross-section projecting portion 81. Portion 81 has a sidewall 82 which is aligned with inner surface 80 of die 66. Sidewall 82 terminates at its upper end in curling contour 84 having a radius equal to that ultimately desired in the rimmed opening- During operation of this apparatus,- a container body is mounted on support die 66. If support die 66 is the same die as was used for hemming, the container body will already be in place. Outer surface 67 supports sidewall 44 and ledge 46. Curling die 80 has its sidewall 82 aligned with the inner surface of post sidewall 26. It is moved so that contour 84 curls sidewall 26 moving edge inwardly and upwardly to provide finished rim 90.

FIG. 8 shows a container resulting from processing with the apparatus of FIGS. 3 and 5-7. The inner diameter of the post portion of the container is one inch. The radius of the hem 92 is approximately 0.03 inches. The radius of the final curl 94 is approximately 0.05 inches. Thus the radius of the hem is approximately 60 percent of the radius of the final curl; The flare on the curl defines a circle of 1.22 inch diameter. The distance 96 between parallel planes through the lowermost portion of the curl and the uppermost portion of the curl is 0.125 inches. The distance 98'between a plane through the lowermost portion of the curl and a parallel plane through the edge turned within the curl is 0.055 inches. The depicted rimmed open-ended container is made from continuously annealed stock without splitting occurring.

FIG. 9 depicts a container resulting from a suitable variation of the second curling step in which the sidewall islcurled outwardly so that edge 63 moves inwardly by not upwardly.

Other materials, methods and apparatus from those specifically described can be used in carrying out this invention. The container may be of any sheet metal commonly used for containers. The blanking apparatus need not be vertically. oriented as shown in FIG. 3 but can be, for example, horizontally oriented or oriented in inclined fashion. Either or both of the dies of the blanking apparatus can move. The interconnecting portion of the support die can be of configurations other than those depicted in FIGS. 3 and 4 as long as it is substantially contoured to the inner surface of the curved portion of the container body to provide support as described earlier. For example, the interconnecting portion can be partly beveled and partly rounded. The described dies can be used in conjunction with conventional die machinery. Thus the scope of the invention is to be determined from the appended claims.

What is claimed is:

1. In the manufacture of an open-ended container from a unitary drawn sheet metal container body of cup-shaped configuration having a substantially circular endwall joined at its periphery by a curved portion to a sidewall, apparatus for blanking the full diameter of the endwall while avoiding dog-legging of the sidewall and to provide a container body sidewall which is tapered in the direction of its edge to facilitate curling of the sidewall in the vicinity of the edge comprising a support die for insertion into said container body, the support die having an endwall, a sidewall, and an interconnecting portion, the interconnecting portion being dimensioned to be substantially contoured to the inner surface of the curved portion of the container body when the support die is in inserted position; cutting die for positioning outside the container body, the cutting die having a uni-diameter circular. recessed portion opposite the endwall of the support die bounded by a cutting edge aligned with the sidewall of the support die; and

means to move at least one of said dies toward the other of said dies to complete the blanking operation.

2. A full diameter blanking apparatus as recited in claim 1 wherein the interconnecting portion of the support die is outwardly convex with the radius of such,

convex portion substantially conforming to the radius of the inner surface of the curved portion of the container body.

3. A full diameter blanking apparatus as recited in claim 1 wherein the interconnecting portion of the sup- 5 port die is beveled so that when the die is in working position the beveled portion is opposite the inner surface of the curved portion of the container body.

4. Method of forming a rimmed opening in a unitary drawn sheet metal container-body of cup-shaped con- 0 figuration and having a substantially circular endwall joined at its periphery by a curved portion to a sidewall comprising the steps of mounting a container body on a support die which has an endwall and a sidewall and a portion interconnecting these two, such support die being dimensioned so that its interconnecting portion is substantially contoured to the inner surface of said curved portion when the container body is mounted on the support die, providing a cutting die havinga uni-diameter circular recessed portion opposite the endwall of the support die bounded by a cutting edge aligned with t sid w l fthe 0 dc; cut ti r ig a fuii d iamet r %qar iit by moving at least one of said dies toward the other while avoiding doglegging of the sidewall of the container body and providing a container body sidewall with an upper tapered edge portion;

moving the tapered edge portion outwardly and downwardly to form a curl with a radius which is less than 75 percent of the radius of the ultimate curl desired at the rimmed opening being formed; and then curling the sidewall to the ultimate radius so that the tapered edge portion is moved inwardly.

5. The method of claim 4 wherein the initial curl has a radius less than 65 percent of the radius of the ultimate curl desired.

6. The method of claim 5 including in the second curling step movement of the tapered edge portion upwardly after it has been moved inwardly. 

1. In the manufacture of an open-ended container from a unitary drawn sheet metal container body of cup-shaped configuration having a substantially circular endwall joined at its periphery by a curved portion to a sidewall, apparatus for blanking the full diameter of the endwall while avoiding dog-legging of the sidewall and to provide a container body sidewall which is tapered in the direction of its edge to facilitate curling of the sidewall in the vicinitY of the edge comprising a support die for insertion into said container body, the support die having an endwall, a sidewall, and an interconnecting portion, the interconnecting portion being dimensioned to be substantially contoured to the inner surface of the curved portion of the container body when the support die is in inserted position; a cutting die for positioning outside the container body, the cutting die having a uni-diameter circular recessed portion opposite the endwall of the support die bounded by a cutting edge aligned with the sidewall of the support die; and means to move at least one of said dies toward the other of said dies to complete the blanking operation.
 2. A full diameter blanking apparatus as recited in claim 1 wherein the interconnecting portion of the support die is outwardly convex with the radius of such convex portion substantially conforming to the radius of the inner surface of the curved portion of the container body.
 3. A full diameter blanking apparatus as recited in claim 1 wherein the interconnecting portion of the support die is beveled so that when the die is in working position the beveled portion is opposite the inner surface of the curved portion of the container body.
 4. Method of forming a rimmed opening in a unitary drawn sheet metal container body of cup-shaped configuration and having a substantially circular endwall joined at its periphery by a curved portion to a sidewall comprising the steps of mounting a container body on a support die which has an endwall and a sidewall and a portion interconnecting these two, such support die being dimensioned so that its interconnecting portion is substantially contoured to the inner surface of said curved portion when the container body is mounted on the support die, providing a cutting die having a uni-diameter circular recessed portion opposite the endwall of the support die bounded by a cutting edge aligned with the sidewall of the support die; cutting a full diameter blank by moving at least one of said dies toward the other while avoiding dog-legging of the sidewall of the container body and providing a container body sidewall with an upper tapered edge portion; moving the tapered edge portion outwardly and downwardly to form a curl with a radius which is less than 75 percent of the radius of the ultimate curl desired at the rimmed opening being formed; and then curling the sidewall to the ultimate radius so that the tapered edge portion is moved inwardly.
 5. The method of claim 4 wherein the initial curl has a radius less than 65 percent of the radius of the ultimate curl desired.
 6. The method of claim 5 including in the second curling step movement of the tapered edge portion upwardly after it has been moved inwardly. 